1 files changed, 281 insertions, 0 deletions

diff --git a/src/lib/util/tun.c b/src/lib/util/tun.c
new file mode 100644
index 000000000..c4ac6ff88
--- /dev/null
+++ b/src/lib/util/tun.c
@@ -0,0 +1,281 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2010, 2011, 2012 Christian Grothoff
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     or (at your option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     Affero General Public License for more details.
+
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+
+/**
+ * @file tun/tun.c
+ * @brief standard IP calculations for TUN interaction
+ * @author Philipp Toelke
+ * @author Christian Grothoff
+ */
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+
+/**
+ * IP TTL we use for packets that we assemble (8 bit unsigned integer)
+ */
+#define FRESH_TTL 64
+
+
+/**
+ * Initialize an IPv4 header.
+ *
+ * @param ip header to initialize
+ * @param protocol protocol to use (e.g. IPPROTO_UDP)
+ * @param payload_length number of bytes of payload that follow (excluding IPv4 header)
+ * @param src source IP address to use
+ * @param dst destination IP address to use
+ */
+void
+GNUNET_TUN_initialize_ipv4_header (struct GNUNET_TUN_IPv4Header *ip,
+                                   uint8_t protocol,
+                                   uint16_t payload_length,
+                                   const struct in_addr *src,
+                                   const struct in_addr *dst)
+{
+  GNUNET_assert (20 == sizeof(struct GNUNET_TUN_IPv4Header));
+  GNUNET_assert (payload_length <=
+                 UINT16_MAX - sizeof(struct GNUNET_TUN_IPv4Header));
+  memset (ip, 0, sizeof(struct GNUNET_TUN_IPv4Header));
+  ip->header_length = sizeof(struct GNUNET_TUN_IPv4Header) / 4;
+  ip->version = 4;
+  ip->total_length =
+    htons (sizeof(struct GNUNET_TUN_IPv4Header) + payload_length);
+  ip->identification =
+    (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, 65536);
+  ip->ttl = FRESH_TTL;
+  ip->protocol = protocol;
+  ip->source_address = *src;
+  ip->destination_address = *dst;
+  ip->checksum =
+    GNUNET_CRYPTO_crc16_n (ip, sizeof(struct GNUNET_TUN_IPv4Header));
+}
+
+
+/**
+ * Initialize an IPv6 header.
+ *
+ * @param ip header to initialize
+ * @param protocol protocol to use (e.g. IPPROTO_UDP), technically "next_header" for IPv6
+ * @param payload_length number of bytes of payload that follow (excluding IPv6 header)
+ * @param src source IP address to use
+ * @param dst destination IP address to use
+ */
+void
+GNUNET_TUN_initialize_ipv6_header (struct GNUNET_TUN_IPv6Header *ip,
+                                   uint8_t protocol,
+                                   uint16_t payload_length,
+                                   const struct in6_addr *src,
+                                   const struct in6_addr *dst)
+{
+  GNUNET_assert (40 == sizeof(struct GNUNET_TUN_IPv6Header));
+  GNUNET_assert (payload_length <=
+                 UINT16_MAX - sizeof(struct GNUNET_TUN_IPv6Header));
+  memset (ip, 0, sizeof(struct GNUNET_TUN_IPv6Header));
+  ip->version = 6;
+  ip->next_header = protocol;
+  ip->payload_length = htons ((uint16_t) payload_length);
+  ip->hop_limit = FRESH_TTL;
+  ip->destination_address = *dst;
+  ip->source_address = *src;
+}
+
+
+void
+GNUNET_TUN_calculate_tcp4_checksum (const struct GNUNET_TUN_IPv4Header *ip,
+                                    struct GNUNET_TUN_TcpHeader *tcp,
+                                    const void *payload,
+                                    uint16_t payload_length)
+{
+  uint32_t sum;
+  uint16_t tmp;
+
+  GNUNET_assert (20 == sizeof(struct GNUNET_TUN_TcpHeader));
+  GNUNET_assert (payload_length + sizeof(struct GNUNET_TUN_IPv4Header)
+                 + sizeof(struct GNUNET_TUN_TcpHeader) ==
+                 ntohs (ip->total_length));
+  GNUNET_assert (IPPROTO_TCP == ip->protocol);
+
+  tcp->crc = 0;
+  sum = GNUNET_CRYPTO_crc16_step (0,
+                                  &ip->source_address,
+                                  sizeof(struct in_addr) * 2);
+  tmp = htons (IPPROTO_TCP);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint16_t));
+  tmp = htons (payload_length + sizeof(struct GNUNET_TUN_TcpHeader));
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint16_t));
+  sum =
+    GNUNET_CRYPTO_crc16_step (sum, tcp, sizeof(struct GNUNET_TUN_TcpHeader));
+  sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+  tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+void
+GNUNET_TUN_calculate_tcp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
+                                    struct GNUNET_TUN_TcpHeader *tcp,
+                                    const void *payload,
+                                    uint16_t payload_length)
+{
+  uint32_t sum;
+  uint32_t tmp;
+
+  GNUNET_assert (20 == sizeof(struct GNUNET_TUN_TcpHeader));
+  GNUNET_assert (payload_length + sizeof(struct GNUNET_TUN_TcpHeader) ==
+                 ntohs (ip->payload_length));
+  GNUNET_assert (IPPROTO_TCP == ip->next_header);
+  tcp->crc = 0;
+  sum = GNUNET_CRYPTO_crc16_step (0,
+                                  &ip->source_address,
+                                  2 * sizeof(struct in6_addr));
+  tmp = htonl (sizeof(struct GNUNET_TUN_TcpHeader) + payload_length);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint32_t));
+  tmp = htonl (IPPROTO_TCP);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint32_t));
+  sum =
+    GNUNET_CRYPTO_crc16_step (sum, tcp, sizeof(struct GNUNET_TUN_TcpHeader));
+  sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+  tcp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+void
+GNUNET_TUN_calculate_udp4_checksum (const struct GNUNET_TUN_IPv4Header *ip,
+                                    struct GNUNET_TUN_UdpHeader *udp,
+                                    const void *payload,
+                                    uint16_t payload_length)
+{
+  uint32_t sum;
+  uint16_t tmp;
+
+  GNUNET_assert (8 == sizeof(struct GNUNET_TUN_UdpHeader));
+  GNUNET_assert (payload_length + sizeof(struct GNUNET_TUN_IPv4Header)
+                 + sizeof(struct GNUNET_TUN_UdpHeader) ==
+                 ntohs (ip->total_length));
+  GNUNET_assert (IPPROTO_UDP == ip->protocol);
+
+  udp->crc =
+    0; /* technically optional, but we calculate it anyway, just to be sure */
+  sum = GNUNET_CRYPTO_crc16_step (0,
+                                  &ip->source_address,
+                                  sizeof(struct in_addr) * 2);
+  tmp = htons (IPPROTO_UDP);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint16_t));
+  tmp = htons (sizeof(struct GNUNET_TUN_UdpHeader) + payload_length);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint16_t));
+  sum =
+    GNUNET_CRYPTO_crc16_step (sum, udp, sizeof(struct GNUNET_TUN_UdpHeader));
+  sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+  udp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+void
+GNUNET_TUN_calculate_udp6_checksum (const struct GNUNET_TUN_IPv6Header *ip,
+                                    struct GNUNET_TUN_UdpHeader *udp,
+                                    const void *payload,
+                                    uint16_t payload_length)
+{
+  uint32_t sum;
+  uint32_t tmp;
+
+  GNUNET_assert (payload_length + sizeof(struct GNUNET_TUN_UdpHeader) ==
+                 ntohs (ip->payload_length));
+  GNUNET_assert (payload_length + sizeof(struct GNUNET_TUN_UdpHeader) ==
+                 ntohs (udp->len));
+  GNUNET_assert (IPPROTO_UDP == ip->next_header);
+
+  udp->crc = 0;
+  sum = GNUNET_CRYPTO_crc16_step (0,
+                                  &ip->source_address,
+                                  sizeof(struct in6_addr) * 2);
+  tmp = htons (sizeof(struct GNUNET_TUN_UdpHeader)
+               + payload_length); /* aka udp->len */
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint32_t));
+  tmp = htons (ip->next_header);
+  sum = GNUNET_CRYPTO_crc16_step (sum, &tmp, sizeof(uint32_t));
+  sum =
+    GNUNET_CRYPTO_crc16_step (sum, udp, sizeof(struct GNUNET_TUN_UdpHeader));
+  sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+  udp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+void
+GNUNET_TUN_calculate_icmp_checksum (struct GNUNET_TUN_IcmpHeader *icmp,
+                                    const void *payload,
+                                    uint16_t payload_length)
+{
+  uint32_t sum;
+
+  GNUNET_assert (8 == sizeof(struct GNUNET_TUN_IcmpHeader));
+  icmp->crc = 0;
+  sum =
+    GNUNET_CRYPTO_crc16_step (0, icmp, sizeof(struct GNUNET_TUN_IcmpHeader));
+  sum = GNUNET_CRYPTO_crc16_step (sum, payload, payload_length);
+  icmp->crc = GNUNET_CRYPTO_crc16_finish (sum);
+}
+
+
+/**
+ * Check if two sockaddrs are equal.
+ *
+ * @param sa one address
+ * @param sb another address
+ * @param include_port also check ports
+ * @return #GNUNET_YES if they are equal
+ */
+int
+GNUNET_TUN_sockaddr_cmp (const struct sockaddr *sa,
+                         const struct sockaddr *sb,
+                         int include_port)
+{
+  if (sa->sa_family != sb->sa_family)
+    return GNUNET_NO;
+
+  switch (sa->sa_family)
+  {
+  case AF_INET: {
+      const struct sockaddr_in *sa4 = (const struct sockaddr_in *) sa;
+      const struct sockaddr_in *sb4 = (const struct sockaddr_in *) sb;
+      if ((include_port) && (sa4->sin_port != sb4->sin_port))
+        return GNUNET_NO;
+      return(sa4->sin_addr.s_addr == sb4->sin_addr.s_addr);
+    }
+
+  case AF_INET6: {
+      const struct sockaddr_in6 *sa6 = (const struct sockaddr_in6 *) sa;
+      const struct sockaddr_in6 *sb6 = (const struct sockaddr_in6 *) sb;
+
+      if ((include_port) && (sa6->sin6_port != sb6->sin6_port))
+        return GNUNET_NO;
+      return(
+        0 == memcmp (&sa6->sin6_addr, &sb6->sin6_addr, sizeof(struct
+                                                              in6_addr)));
+    }
+
+  default:
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+}
+
+
+/* end of tun.c */